A large sized proximity type image intensifier tube has been developed and is the subject of U.S. Pat. Nos. 4,140,900; 4,255,666 and 4,730,107. In this type of proximity image intensifier tube, at least one stage of amplification is provided between an inwardly concave metallic input window and a phosphor output screen deposited on a glass output viewing window. Each amplification stage includes a photocathode carrying substrate supported in a ring and suspended within a metallic tube envelope on insulating rods attached to the ring. A high voltage is applied to the substrate assembly through one of the insulated support rods to create a high voltage potential between the substrate assembly and the metallic tube envelope. Such a suspension system is more fully described in U.S. Pat. No. 4,315,183 to Merritt and which is incorporated herein by reference.
The substrate assembly is supported against a shoulder of the support ring and is mounted by way of many parts, most of which require special coating to prevent gauling. Threaded aluminum studs in the support ring shoulder area are pressed into the support ring around its circumference. Spring holders and pin holders are fixed to the support ring by way of the threaded studs by nuts torqued to specific values. The substrate assembly is radially aligned within the support ring by a plurality of wavy springs. Each spring is attached to a spring holder and applies radial force to the outer perimetral edge of the substrate assembly. At each contact point between a spring portion and the edge of the substrate assembly, a high voltage contact is placed.
The high voltage contacts include a plurality of metal U-shaped channel portions each of which extend over a small portion of the circumference of the substrate assembly and fit between the spring contact and the perimetral edge of the substrate assembly. To complete the assembly, a circular cover plate fits on the opposite side of the substrate assembly to capture it against the shoulder of the support ring. A plurality of screws attach the cover plate to the support ring.
Many disadvantages attain from this substrate support assembly. Well over 50 separate parts, many of which need to be specially coated are required to complete the assembly. Since threaded parts are used, many sharp edges are presented and are the possible source for undesirable high voltage emission and extraneous particles. Vibration and shock testing at possible and probable levels of transport and handling have shown that the electrodes tend to move around in the support. This undesired movement may create or dislodge extraneous particles within the tube envelope. Since shocks and vibrations are amplified, the tube is more sensitive to mechanical disturbances.
It is therefore an object of this invention to overcome the above mentioned problems and others by providing an improved component support for use in vacuum tubes and in particular a substrate support for use in proximity type image intensifier tubes.